Last we heard from Boston Dynamics' Cheetah, it was coursing along at 18 miles per hour, the fastest a robot had ever run. Now, inspired perhaps by Olympic sprinters, it's cranked that up to a frightening 28.3 MPH.

Usain Bolt's peak speed during the 100-meter dash was 27.78 MPH. Now even our best humans falter before the inexorable scamper of the legged machines.

Cheetah, for now, is tethered to an external power supply, and runs on an indoor treadmill. Next year, however, Boston Dynamics plans to unleash Wildcat